Project summary: In addition to the concept of discovering multiple chromosomal transcripts for opioid receptors, this project will look into a detailed analysis of the site-directed mutagenesis of the opioid receptor binding site. This project was temporarily set aside with the sudden departure of our postdoctoral fellow in June, 1998. We are currently searching for another replacement with experience in molecular biology. Preliminary data in 1998 suggested that the brain of the dipoid teleost Mummichog contained two distinct transcripts for each of the opioid receptors, delta, mu and kappa. Partial sequence analyses indicated that they differed to a greater degree from each other than to that of the human receptor cDNA. The importance of continuing this research cannot be underestimated since the formation of a recent knockout mouse for the delta opioid receptor revealed that the brain contains another type of delta receptor heretofore unrecognized that differs from that in the periphery. - Molecular biology, cDNA, DNA sequencing, P-glycoproteins, RNA library, fish brain; opioid receptors